Think in terms of the mixing box/throttle body. Let off the foot throttle and the butterfly valve in the mixing box closes, but the engine is still spinning. The governor valve in the mixing box then "wanders" until the pressure in the intake manifold stabilizes. The end result is that the spring in the governor vacuum box beats the diaphragm and shoots some extra fuel. Even if the governor system was working perfectly you create a fuel rich situtation because nothing reacts instantaneously. A moderate black puff is normal in a non-pollution controlled engine, but assumes that the engine breathing systems are normal.

You will need a wire feed welder, preferably with an inert gas attachment. This feeds a mixture of carbon dioxide and argon over the weld while you have the arc lit and prevents the metal from catching fire and cools it faster. You will also need heavy cotton pants and long sleeve shirt, leather gloves, and a good welder's helmet. Don't save money on the eye shield, your eyes arent' worth it!

If you don't have ANY experience with welding, find someone who does and ask for help/advice. You can seriously damage your eyes and skin arc welding, I would SERIOUSLY recommend you have someone teach you. It's also an art, so expect to practice some and/or make some messes before you get good at it.

I don't mean to discourage you, just get someone who knows what they are doing to teach you! You can get a 110 V system for a couple hundred dollars that will work just fine for you -- after all, you don't need a 100% duty cycle monster welder to fix one car!

And all my diesels blow a little puff of black smoke when I let off the throttle suddenly.

Where can I get a mig welder for $200? I see little buzz boxes all the time for between $100-$200 but never see anyone selling a mig. I end up using one at some local sign shops when I need it but having my own would be nice. I can weld, but no way good enough to stick weld sheet metal.

cool. All I have ever seen or used are the big industrial wire feed continuous use units with the large tanks of argon for aluminum or co2/argon mix for steel wire. Had no idea the little boxes could handle gun setups. I am going to have to check this out. Already have the gloves, helmet, and leathers for everything else.
PS the hood comes in real handy for looking at a solar eclipse and or sun spot activity

Have been welding on my own projects (used to do it for Money) for 40 years and Peter is right you dont just pick up a welder wire or stick and get good welds on thin metal.If you plan to do much restoration work on cars a begining welding class at a comunity College will be the best thing you ever did.And DON'T buy an el cheapo wire welder they tangle wire worse than a left handed casting reel.Also look in factory manual before welding on any computerised cars......
William Rogers...... P.S. after 40 years I can weld body panels with a buzz box if thats all there is to work with........